Ink composition for continuous deflected jet printing

ABSTRACT

An ink composition for continuous deflected ink jet printing, liquid at ambient temperature is disclosed. One aspect is an ink composition comprising: a solvent including organic solvent compound(s), and optionally water, the solvent representing at least 20 % by weight of the total weight of the ink. Furthermore, there is at least one compound imparting conductivity to the ink composition, chosen from among the ionic liquids, the compound representing 0.2 % by weight to 4 % by weight of the total weight of the ink composition, preferably 0.5 to 3 % by weight of the total weight of the ink composition. Lastly, the ink composition includes less than 10 % by weight, preferably less than 5 % by weight, more preferably less than 1 % by weight, and most preferably 0 % by weight of water relative to the total weight of the ink composition.

This application is a Continuation Application of U.S. Application No.14/003142, filed Nov. 18, 2013, which is a U.S. National Phase ofInternational Application No.: PCT/EP2012/054025, filed Mar. 8, 2012,which claims the benefit of French Patent Application No. 11 51938 filedMar. 9, 2011, and U.S. Provisional

Pat. Application No. 61/495,869 filed on Jun. 10, 2011 each of which isincorporated by reference in their entirety.

The invention relates to an ink composition for marking supports,substrates and objects of all types, the properties of which areparticularly suitable for liquid jet printing or marking and veryparticularly for the continuous deflected inkjet marking of a very largevariety of supports, substrates, and objects, whether porous ornon-porous.

Inkjet printing is a well known technique, which allows the printing,marking or decoration of all types of objects, at high speed, andwithout these objects coming into contact with the printing device, withmessages that can be varied at will, such as bar codes, sell-by dates,etc., and even on non-planar supports.

Inkjet printing systems can be divided into two main types: “Drop ondemand” (DOD) or “continuous jet” (CJ) .

We are interested more particularly in the latter technique, morespecifically in the continuous deflected jet technique.

Continuous deflected jet spraying consists in sending ink, underpressure, into a cavity containing a piezoelectric crystal, from wherethe ink escapes via an orifice (nozzle) in the form of a jet. Thepiezoelectric crystal, vibrating at a given frequency, causes pressuredisturbances in the inkjet, which oscillates and gradually breaks upinto spherical drops or droplets. An electrode, placed in the path ofthe jet, where it breaks up, makes it possible to give these drops anelectrostatic charge, if the ink is conductive. The drops thus chargedare deflected in an electric field and allow the printing.

The drops that are not charged, and therefore are not deflected, arerecovered in a gutter, drop collector, where the ink is sucked up, thenrecycled to the ink circuit.

This type of inkjet spraying provides contactless marking at highthroughput speed on objects that are not necessarily planar and with thepossibility of changing the message at will. The technique isparticularly suited for the marking and identification (expiry dates,serial numbers, batch numbers, bar codes etc.) of industrial products onproduction lines.

The described field of application requires varied ink formulations,adapted to the variety of substrates to be marked (metal, plastics,glass, etc.) and meeting a large variety of industrial constraints inparticular those in which the water-resistance of the marking is ofimportance.

Ink compositions suitable for continuous deflected jet spraying mustsatisfy a certain number of criteria inherent in this technique,relating, inter alia, to the viscosity, the electrical conductivity, thesolubility in a solvent for cleaning, the compatibility of theingredients, the correct wetting of the supports to be marked, etc.

Moreover, these inks must dry rapidly, be capable of passing through thenozzle without blocking it, with a high stability of orientation of thejet while at the same time allowing easy cleaning of the print head.

The ingredients that make up current inks, for the inkjet of thecontinuous deflected jet type, are organic or mineral products; they aredyestuffs, such as dyes or pigments, resins or binders, in one or moresolvent (s) that is (are) more or less volatile, or in water, andoptionally one or more conductivity salt(s), and also various additives.

The dyestuffs are known as “dyes or pigments” depending on whether theyare respectively soluble or insoluble in the solvent used.

The pigments, which are by nature insoluble, are therefore dispersed andmay be opaque or non-opaque. They give the ink its colour, its opacity,or specific optical properties, such as fluorescence (see patents orpatent applications US-A-4 153 593, US-A-4 756 758, US-A-4 880 465,EP-A-0 289 141, US-A-5 395 432, GB-A-2 298 713). In certain cases, thedyes themselves also impart the ink sufficient conductivity for it notto be necessary to add a conductivity salt. The dyes known under thename C.I. Solvent Black 27, 29, 35 and 45 are included in this case.

The binder(s) or resin(s) is (are) generally, for the most part, one (ormore) solid and polymeric compound(s) and the choice thereof is dictatedby their solubility in the selected solvents and by their compatibilitywith the dyes and the other additives, but also and especially as afunction of the properties that they impart to the film of ink, once dry(see patents or patent applications US-A-4 834 799, GB-A-2 286 402,US-A-5 594 044, US-A-5 316 575, WO-A-96/23844, WO-A-95/29 287).

Their primary function is to provide the ink with adhesion to themaximum number of supports or to specific supports, for examplenon-porous supports. They also make it possible to give the ink adequateviscosity for the formation of the drops from the jet and they providethe ink, or rather the marking obtained, with most of its properties ofresistance to physical and/or chemical attacks.

The solvent of these inks is constituted, most often, of a mixturecomprising, on the one hand, a predominant amount of volatile and notvery viscous solvents, in order to make it possible for the markings todry very rapidly and to adjust the viscosity to the desired value, forexample from 2 to 10 mPa.s and, on the other hand, more viscous and lessvolatile solvents that dry more slowly, in a lesser amount, in order toprevent the ink from drying in the nozzle when the printing machine isshut down (see patents or patent applications US-A-4 155 767, WO-A-9214794, WO-A-92 14 795 and US-A-4 260 531).

The volatile solvents used most often are alcohols, ketones or esters oflow molecular weight, as is indicated in patents US-A-4 567 213 andUS-A-5 637 139. Among these solvents, mention may essentially be made ofmethanol, ethanol, 1-propanol and 2-propanol, acetone, methyl ethylketone (“MEK”), and methyl isobutyl ketone.

The less volatile solvents which particularly have a delayed dryingfunction are most often ketones such as cyclohexanone, glycol etherscited in documents US-A-4,024, 096 and US-A-4,567,213, ethers andacetals such as furan or dioxane mentioned in document US-A-4,155,767,dimethyl formamide or dimethylsulfoxide (US-A-4,155,895), lactones(EP-A-0 034 881), N-methyl pyrrolidone (EP-A-0 735 120), glycols(WO-A-96 23844), and even aliphatic hydrocarbons (US-A-4,166,044) oreven water, alone or in combination with other solvents cited above; inthis respect, reference may be made to documents US-A-4,153,593, GB-A-2277 094 and FR-A-2 460 982.

In general, the main or majority predominant solvents in inks intendedfor deflected continuous jet printing must meet a certain number ofcriteria, in particular:

-   their volatility must be sufficient so that the ink dries rapidly on    the substrate, support to be marked but not too volatile so that it    does not evaporate too quickly in the printer, in particular when    printers are not in operation;-   their solvent property regarding the binders of the ink, dyes or    pigment dispersions and regarding the support to be printed, must    allow good adhesion to be imparted to the dry ink;-   their effects on the health of persons namely their toxicity,    noxiousness, irritant or inflammable nature must be limited;-   they must allow an ink, which may optionally be intended to be    ingested, to be kept sterile;-   finally, they must have the capacity to maintain the ionic species,    such as salts, which impart conductivity to the ink, dissolved and    dissociated.

The additives comprise dispersants which allow dispersion of pigments,surfactants which modify the wettability or penetrability of the ink(US-A-5 395 431), in particular those which modify or control the staticor dynamic surface tension such as Fluorad® FC 430 from 3M®, agents thatinhibit the corrosion induced by the salts providing conductivity (seedocuments EP-A-0 510 752, US-A-5 102 458), or else additives thatprotect the ink against the proliferation of bacteria and of othermicroorganisms: these are biocides, bactericides, fungicides and thelike, which are particularly useful in inks that contain water, pHcontrol buffers (see EP-A-0 735 120), and anti-foaming agents.

The optional conductivity salt(s) provide(s) the ink with theconductivity for the electrostatic deflection. Reference may be made onthis subject to document US-A-4,465,800.

Among the salts which impart conductivity, all kinds of species are usedthat are ionisable, soluble and may be dissociated in the solvent mediumof the ink.

For inks in which the majority, predominant solvent is water, impartingconductivity to the ink does not generally give rise to any problem,since most water-soluble products are ionisable species.

However, an aqueous medium does not allow a large variety offormulations, since the solvent property of water is limited, and therate of evaporation of water is too slow to benefit from thepossibilities of printing at high speed as allowed by ink-jet printing.In addition, the variety of organic solvents with high dissolving powerfor polymers and dyes allows the formulating of rapid drying inks havingexcellent adhesion to all kinds of substrates.

On the other hand, in these organic media, conductivity is only possiblewhen the solvents have sufficient dissociating properties i.e. whentheir dielectric permittivity and dipole moment are sufficiently high.If this is the case, a salt must be found whose cation and anion aresufficiently soluble in the medium.

A large amount of scarcely conductive salt may have a negative effect onthe functioning of the printer through clogging of the nozzle when theprinter is not in operation (cf. EP-A-0 850 281, page 8, line 21) sincethese salts have a tendency to crystallize when their concentration istoo close to their solubility limit.

Among the salts commonly used are those whose cation is an alkalinemetal such as Lithium, Sodium, Potassium (US-A-3,994,736) oralkaline-earth (US-A-4,070,322, US-A-4, 680, 058) ; the salts ofammonium, of tetra-alkyl ammonium e.g. tetrabutylammonium(WO-A-00/63305), of hydroxylamine, dimethylamine (US-A-4,465,800), ofdiethylamine or morpholine (US-A-4,155,767), of the chromophore part ofbasic dyes (EP-A-0 034 881); and some amine salts (US-A-4,567,213) ortetra-alkyl phosphonium salts (US-A-5,755,860) in which the 4 alkylgroups are identical. Among the different types of anions, mention ismade of the halides such as chlorides, bromides (US-A-5,693,127),iodides (US-A-5,637,139); nitrates; thiocyanates (US-A-4,024,096);formiates; acetates; propionates; sulfonates such as the para-toluenesulfonates (EP-A-0 034 881) or the trifluoromethane sulfonates(US-A-6,251,175); tetrafluoroborates (WO-A-00/63305); bicarbonates;citrates; lactates and alginates (US-A-5,800,601); hydroxides(WO-A-00/22055); sulfates; phosphates (US-A-5,443,628);hexafluorophosphates; hexafluoroantimonates; the diazonium, iodonium,sulfonium, selenonium, sulfoxonium, or arsonium salts (US-A-7, 147,801).

The choice of salts is guided by:

-   their capacity to impart conductivity to the ink at the lowest    possible level;-   their solubility;-   their corrosiveness for the constituent metals of printers;-   their chemical compatibility/inertia vis-àvis the other ink    components (see EP-A-0 465 039);-   their volatility;-   their solubility in water which may be desirable or harmful, for    example regarding the water resistance of the ink;-   their cost per unit of conductivity provided.

Most of the above-cited salts have a certain number of disadvantages,for example:

-   the halides, fluorides, chlorides and to a lesser extent the    bromides and iodides have a very marked corrosive nature, to the    extent that anti-corrosion additives are needed to limit the effect    thereof. Secondary amines have been claimed in patent US-A-5,102,458    (EP-A-0 510 752), and dinonylnaphtalene sulfonates mentioned in    document US-A-5,270,368, in order to limit corrosion;-   the salts which are sufficiently soluble in the least polar    solvents, such as ketones, are few;-   not all the possible salts are compatible with all the ink    ingredients, in particular the inorganic salts and notably the    inorganic cations such as Na, K, Li, Mg have a mineral nature making    them little compatible with the binders such as resins, and the    other organic ingredients of the ink;-   some cations such as the ammonium ion are volatile and disappear    progressively when the ink is recirculated in printers of continuous    inkjet type. The same applies to some acetates and formiates;-   the cations of tetra-alkyl ammonium type are of high molecular    weight, and on this account they have reduced efficacy per unit of    weight. Those with the lowest molecular weight are scarcely soluble    in ketones and are of high cost;-   the amines such as those added to limit the corrosion caused by some    salts are products which react slowly with ketones and are therefore    destroyed. They cannot be used in ink formulations containing ketone    solvents without the risk of parasitic reactions;-   complexing compounds such as crown ethers have been proposed (EP-A-1    858 990) to dissociate and thereby improve the solubilisation of    inorganic cation salts such as lithium, sodium or potassium. The    cost of such complexing agents may be very high and they do not    provide a reliable solution to the problems relating to the    crystallization of conductivity salts.-   the salts, on account of their ionic nature are generally    water-soluble, they make the inks too hydrophilic and reduce the    water resistance of the inks;-   even if some salts are well dissociated in the medium, their    solubility limit may be low and the risks of precipitation are high.

The salts used to date are solids which tend to crystallize easily. Theformation of such crystals causes major defects in printers, such asclogging of nozzle filters and of any orifice of small diameter. Onefundamental criterion which conductivity salts must meet is thereforethe absence of crystallization, precipitation of these salts.

In order to comply with this last, important criterion, lengthystability studies on complete formulations of inks are needed to verifythat no precipitation of these conductivity salts, either alone or incombination with other ink ingredients, takes place over time at all thestorage temperatures of inks or at all printer operating temperatures.

It is known that, in general, the solubility of salts at low temperatureis reduced and the risks of precipitation or crystallization areincreased.

It follows from the foregoing that very few salts simultaneously meetall the above-mentioned criteria and requirements.

In particular, very few salts are at the same time sufficientlydissociated in scarcely dissociating solvent mixtures to providesufficient conductivity, have little tendency to precipitate orrecrystallize, and are water-insoluble.

The goal of the invention is therefore to provide an ink compositionsuitable in particular for continuous deflected ink jet printing, whichinter alia fulfils all the above-indicated needs, which meets theabove-mentioned criteria and requirements, which does not have thedisadvantages, limitations, defects and shortcomings of prior art inkcompositions, and which overcomes the problems of prior art compositionsrelated in particular to the presence of a conductivity salt and morespecifically to the nature of the conductivity salts contained in theseink compositions.

This goal and others are achieved according to the invention by an inkcomposition for continuous deflected ink jet printing that is liquid atambient (room) temperature, comprising:

-   a) a solvent comprising, preferably consisting of, one or more    (non-aqueous) organic solvent compound(s), and optionally water, the    said solvent representing at least 20% by weight of the total weight    of the ink;-   b) at least one compound imparting conductivity to the ink    composition, chosen from among ionic liquids, the said compound    representing 0.2% by weight to 4% by weight of the total weight of    the ink composition, preferably, 0.5 to 3% by weight of the total    weight of the ink composition; and the ink composition comprising    less than 10% by weight, preferably less than 5% by weight, more    preferably less than 1% by weight and most preferably 0% by weight    of water relative to the total weight of the ink composition.

By ambient temperature is generally meant a temperature of 5° C. to 30°C., preferably 10° C. to 25° C., more preferably 15° C. to 24° C.,further preferably 20° C. to 23° C. Evidently the ink is liquid atatmospheric pressure.

Advantageously, the ink composition of the invention may furthercomprise:

-   c) a binder.-   d) one or more dye(s) and/or pigment(s).

Advantageously, the ink composition of the invention may furthercomprise:

Advantageously, the said ionic liquids are chosen from among salts,ionic liquids whose melting point is 100° C. or lower.

Advantageously, the said ionic liquids are chosen from among salts,ionic liquids which are water-insoluble, i.e. soluble in water by notmore than 0.1% by weight at ambient temperature.

Advantageously, the said ionic liquids are chosen from among thenon-symmetrical alkyl-imidazolium, alkylpyridinium or aryl-pyridinium oralkyl-phosphonium salts, substituted pyrrolidinium salts ornon-symmetrical tetra-alkyl ammonium salts, guanidinium salts andmixtures thereof.

Advantageously the said ionic liquids are chosen from among thetriflates, tetrafluoroborates, hexafluorophosphates,paratoluenesulfonates also called tosylates, thiocyanates,bistriflimides (trifluoromethanesulfonylimides), formiates, halides,alkylsulfates, alkylphosphates, alkylsulfonates, methylcarbonates,glycolates, dicyanamides, acetates; of non-symmetricalalkyl-imidazolium, alkyl-pyridinium or aryl-pyridinium oralkyl-phosphonium, of substituted pyrrolidiniums, or of non-symmetricaltetra-alkyl ammoniums, of guanidinium and mixtures thereof.

The ink composition of the invention differs fundamentally from theprior art ink compositions in that the compounds imparting conductivityto the composition are chosen from the products commonly called ionicliquids.

In the ink composition of the invention, the purpose of the ionic liquidis solely to impart electric conductivity to the ink composition in theliquid state for continuous deflected ink jet printing, and mostcertainly not any electric conductivity in the dry state in the markingobtained after drying of the ink composition due to evaporation of thesolvent and/or absorption of the ink composition in the substrate.

The marking obtained with the ink composition of the invention isgenerally not conductive.

The marking obtained contains ionic liquid (which does not evaporate ondrying) but since this ionic liquid is present in the ink composition ofthe invention and hence in the marking obtained, in small quantities, itcannot communicate any conductivity to this marking.

In general, the ink composition of the invention does not contain -ascompound imparting conductivity to the composition- any conductivitysalts such as those commonly used in ink compositions for continuousdeflected ink jet printing.

The composition of the invention therefore overcomes the problemsrelated to the use of conductivity salts in the prior art compositions.

Ionic liquids can be defined as liquid salts comprising a cation and ananion. Ionic liquids are therefore generally composed of a voluminous,bulky, organic cation imparting a positive charge thereto, with which aninorganic anion is associated imparting a negative charge thereto.

In general, the cation has a structure that is sufficientlydissymmetrical to prevent crystallization.

In addition, ionic liquids, as their name suggests, and as indicatedabove, are generally liquid at a temperature of 100° C. or lower, forexample in the temperature range of -60° C. to 100° C., and inparticular at around ambient, room temperature, and they are oftencalled « RTILs » (« Room Temperature Ionic Liquids »).

In other words, the name ionic liquid is often and commonly given to allthe salts defined above whose melting point is generally 100° C. orlower.

Their volatility is practically zero at ambient temperature on accountof their ionic nature.

The books « Ionic Liquids in Synthesis » by Peter Wasserscheid, TomWelton ISBN: 3-527-30515-7 - Wiley-VCH and « Chemistry in AlternativeReaction Media », by D. J. Adams, P. J. Dyson, S. J. Taverner, ISBN:0-471-49849-1 - Wiley describe ionic liquids and the uses thereof.

It has been observed that when the ionic liquid is not soluble in water,the water-resistance of the marking obtained is not only maintained butalso reinforced through their presence.

By ionic liquid non-soluble in water, water-insoluble, is generallymeant that the solubility of this ionic liquid in water is not more than0.1 % by weight (generally measured at ambient temperature and ambientatmospheric pressure).

This increased water-resistance was surprisingly observed moreparticularly with some resins including phenolic resins of novolac type.

The incorporation of the said compounds, ionic liquids, impartingconductivity to ink compositions, in particular into non-aqueous andvolatile ink compositions for continuous deflected ink jet printing, isneither described nor suggested in the prior art.

Ionic liquids are chiefly used as reaction medium to replaceconventional solvents, such as extraction solvents, on account of theirpractically non-existent (quasi-zero) volatility and high solvent(dissolving) and separating power. They are used in particular asbattery electrolytes, as cellulose solvents, or reactive gas absorbers.These are fields far removed from the field of ink compositions.

Ionic liquids have been proposed in aqueous inks for ink jet printing ofthe drop-on-demand type (US-A-6,048,388) .

More specifically, this document concerns an ink composition whichcomprises water, a dye and an ionic liquid. This composition does notcontain any organic solvents.

Ionic liquids have also been proposed as main solvent to replace water,or in combination with water or a solvent (US-A1-2006/0139426 or EP-A1-1676 894).

This document describes ink compositions comprising at least one dye andan ionic liquid.

In these compositions, the ionic liquid acts as solvent and is notintended to impart any conductivity to the ink.

Such compositions, which generally contain a major amount of ionicliquid, could not be used for applications on non-porous substrates forwhich the solvent must evaporate rapidly for adhesion to the substrate,since the ionic liquid is not volatile.

Patent application US-A1-2009/0317549 proposes the use of ionic liquidsfor complexing divalent cations such as calcium.

More specifically, this document describes an essentially aqueouscomposition comprising a water-soluble salt of a divalent metal, acomplexing agent having affinity for the divalent metal such as calcium,and an optical whitening agent.

The complexing agent can be chosen from among numerous families ofcompounds including ionic liquids.

In the compositions of this document, the ionic liquid acts as acomplexing agent of the divalent metal ions in an aqueous medium and isabsolutely not intended to impart any conductivity to the composition.

Patent application US-A1-2008/0209876 proposes the use of ionic liquidsfor dispersing nanoparticles in an organic solvent.

More specifically, this document relates to a solvent compositioncomprising an organic solvent, dispersed nanoparticles and anon-volatile electrolyte which may be an ionic liquid.

There is no mention in this document that these compositions, which aregelled liquid compositions, are compositions which could be used forcontinuous deflected ink jet printing.

Patent application US-A1-2006/0139426 proposes the use of an ionicliquid for dissolving dyes for dyeing operations.

More specifically, this document concerns an ink, in particular an inkfor ink-jet printing which contains a dye and an ionic liquid.

In this document, the ionic liquid is used in high proportions possiblyreaching 95 % by weight, it acts essentially as solvent, as vehicle, andis absolutely not intended to impart any conductivity to thecomposition.

According to the invention, it was ascertained that, surprisingly, ionicliquids incorporated in ink compositions in small quantities, defined bya narrow weight percentage range namely 0.2 % by weight to 4 % by weightof the total weight of the ink composition, could impart necessary andsufficient conductivity to ink formulations for continuous deflected inkjet printing without compromising the stability of these formulations,and optionally imparting improved water-resistance of markings.

In other words, the incorporation of ionic liquids in a small amountnamely from 0.2 % by weight to 4 % by weight of the total weight of theink composition, in the inks of the invention, allows the formulating ofinks with more varied compositions than with the salts used up untilnow.

Persons formulating the ink have available a very wide choice of ionicliquids, much less restricted than the choice of salts currently used.On this account, it is therefore possible to impart to the ink all theproperties that may be desired which were often impossible to obtainwith the salts previously used in ink compositions.

There exists a large variety of ionic liquids which, whilst impartingsufficient conductivity, having little tendency to precipitate orrecrystallize like numerous salts, and preferably being water-insoluble,are also able to impart to the ink a whole series of advantageousproperties.

If a more precise definition is given of the ionic liquid in the inkcomposition according to the invention, by « liquid » it is generallymeant that the ionic liquid is liquid at a temperature equal to or lowerthan 100° C., for example over a temperature range of -60° C. a 100° C.,and that it is notably liquid in the region of ambient temperaturenamely 15° C. to 30° C., preferably 20° C. to 25° C.

There is no limitation regarding the choice of the C⁺ cation of theionic liquid.

Preferably, the C⁺ cation is chosen from among the organic cations, inparticular « voluminous », bulky, organic cations i.e. cationscomprising groups known to the man skilled in the art of organicchemistry for having high steric hindrance.

For example, the C⁺ cation of the ionic liquid can be chosen from amongthe cations: hydroxonium, oxonium, ammonium, amidinium, phosphonium,uronium, thiouronium, guanidinium, sulfonium, phospholium,phosphorolium, Iodonium, carbonium; heterocyclic cations, and thetautomer forms of these cations.

By heterocyclic cations is meant cations derived from heterocyclescompounds i.e. rings comprising one or more hetero-atom(s) generallychosen from among N, O, P and S.

These heterocycles compounds may be saturated, unsaturated or aromatic,and they may also be condensed with one or more other heterocycle(s)and/or one or more other saturated, unsaturated or aromatic carbonring(s).

In other words, these heterocycles may be monocylic or polycyclic.

These heterocycles may also be substituted by one or more substituent(s)preferably chosen from among the straight-chain or branched alkyl groupswith 1 to 20 carbon atoms such as the methyl, ethyl, n-propyl, i-propyl,n-butyl, i-butyl, and t-butyl groups; the cycloalkyl groups with 3 to 7carbon atoms; the straight-chain or branched alkenyl groups with 1 to 20carbon atoms; the straight-chain or branched alkynyl groups with 1 to 20carbon atoms; the aryl groups with 6 to 10 carbon atoms such as thephenyl group; the alkyl- (1 to 20 carbon atoms) - aryl (6 to 10 carbonatoms) groups such as the benzyl group.

The heterocyclic cations may be chosen from among the pyridinium,quinolinium, isoquinolinium, imidazolium, pyrazolium, imidazolinium,triazolium, pyridazinium, pyrimidinium, pyrrolidinium, thiazolium,oxazolium, pyrazinium, piperazinium, piperidinium, pyrrolium,pyrizinium, indolium, quinoxalinium, thiomorpholinium, morpholinium andindolinium cations.

These cations possibly being optionally substituted as defined above.

The heterocyclic cations also include the tautomer forms thereof.

Below are given examples of heterocyclic cations which may form the C⁺cation of the ionic liquid solvent of the electrolyte according to theinvention:

In these formulas, the groups R¹, R², R³ and R⁴, independently of eachother represent a hydrogen atom or a substituent preferably chosen fromamong the groups already listed above, in particular the straight-chainor branched alkyl groups with 1 to 20 C.

The diversity of the ionic liquids is such that it is possible to use alarge number thereof in the ink compositions according to the invention.However, families of ionic liquids are of more interest for use in inkcompositions for continuous deflected ink jet printing. These familiesof ionic liquids are notably defined by the type of C⁺ cation used, andhave been mentioned above.

For example, preferably, the C⁺ cation of the ink composition accordingto the invention is chosen from among non-substituted or substitutedimidazoliums such as di-, tri-, tetra- and penta-alkyl imidazoliums, thequaternary ammoniums, non-substituted or substituted piperidiniums suchas dialkylpiperidiniums, non-substituted or substituted pyrrolidiniumssuch as dialkylpyrrolidiniums, non-substituted or substitutedpyrazoliums, dialkylpyrazoliums, non-substituted or substitutedpyridiniums such as alkylpyridiniums, the phosphoniums,tetraalkylphosphoniums and sulfoniums such as trialkylsulfoniums.

Preferably the C⁺ cation of the ionic liquid is chosen from thepiperidiniums such as the dialkylpiperidiniums, the quaternary ammoniumssuch as the quaternary ammoniums carrying four alkyl groups, and theimidazoliums such as the di-, tri-, tetra- and penta substitutedimidazoliums, for example di-, tri-, tetraand penta-alkyl imidazoliums.

As already specified above, the alkyl groups generally have 1 to 20 Cand may be straight-chain or branched.

Similarly, there is no limitation regarding the choice of the A⁻ anionof the ionic liquid.

Preferably, the A⁻ anion of the ionic liquid may be chosen from amongthe halides such as Cl-, BF₄ ⁻, B (CN)₄ ⁻ , CH₃BF₃ ⁻, CH₂CHBF₃ ⁻, CF₃BF₃⁻, m-C_(n)F_(2n+1)BF₃ ⁻ (where n is an integer such that 1≤_n≤10) , PF₆⁻, CF₃CO₂ ⁻, CF₃SO₃ ⁻, N (SO₂CF₃) ₂ ⁻, N (COCF₃) (SOCF₃) ⁻, N (CN) ₂ ⁻,C (CN) ₃ ⁻, SCN⁻, SeCN⁻ , CuCl₂ ⁻ and AlCl₄ ⁻.

For example 1-ethyl-3-methylimidazolium thiocyanate may be cited whichhas a melting point of lower than -20° C.

The sales documents of the companies BASF©, MERCK©, SIGMA-ALDRICH©,CYTEC©, to which reference may be made, give numerous examples of ionicliquids.

Contrary to prior art compositions which contain high quantities ofionic liquids, since these liquids act essentially as solvents, the inkcomposition of the invention contains a small quantity of ionicliquid(s) defined by a narrow range namely a quantity that is justsufficient to impart the necessary conductivity to the ink, butinsufficient to reduce the volatility of the solvents and hamper thedrying of the ink.

By sufficient quantity is generally meant a quantity that is sufficientto impart to the composition a conductivity that is equal to or higherthan 5 pS/cm, preferably 5 to 5000 pS/cm at 20° C.

Conductivity is measured with a laboratory conductometer, CDM210 modelof Radiometer Analytical.

This sufficient quantity of ionic liquid(s), is according to theinvention, of at least 0.2% by weight of the total weight of ink, and atmost of 4% by weight of the total weight of the ink.

Unlike the compositions of the prior art, the ink composition of theinvention also comprises a very small quantity of water of less than 10% by weight, preferably less than 5 %, more preferably less than 1 % byweight relative to the total weight of the ink.

The ink composition of the invention can even be considered as beingessentially free of water (0 % water).

In fact, the water that is present is only added water present as animpurity in the various components of the ink. The higher the degree ofpurity of the chosen components, the lower the water content.

The low content or absence of water in the ink composition of theinvention promotes the formation of the film of ink when the binders andother dyes of the composition are water-insoluble, thereby improving theresistance and adhesion properties of the ink.

In the composition of the invention the solvent generally represents atleast 20 % by weight of the total weight of the ink composition,preferably the solvent represents 30 to 90 % by weight, more preferably60 to 80 % by weight of the total weight of the ink composition.

The solvent comprises and preferably consists of one or more organicsolvent compound(s) and optionally water provided that the amount ofwater pays heed to the above-indicated conditions.

Advantageously the said organic solvent compound(s) comprise a majority(predominant) proportion by weight of one or more volatile organicsolvent compound(s), and a minority proportion by weight of one or morenon-volatile organic solvent compound(s).

Preferably the solvent consists of (is composed of) one or more volatileorganic solvent compound(s).

By volatile organic solvent compound is generally meant that thiscompound has a rate of evaporation of more than 0.5 on the scale atwhich butyl acetate has a rate of evaporation of 1.

In general, the volatile nature is estimated at ambient atmosphericpressure, namely in general a pressure of one atmosphere, and at ambienttemperature such as already defined above.

The said organic solvent compound(s) forming part of the solvent arechosen for example from among alcohols in particular alcohols with lowmolecular weight, for example aliphatic alcohols such as ethanol;ketones preferably of low molecular weight; the ethers of alkyleneglycols; the esters of alkylene glycols and the esters of ethers ofalkylene glycols such as the acetates; dimethyl formamide; N-methylpyrrolidone; acetals; esters; straight-chain or cyclic ethers;aliphatic, cyclic or straight-chain hydrocarbons; aromatic hydrocarbons;and the carbonates such as propylene carbonate, ethylene carbonate anddimethyl- and diethyl-carbonates; and mixtures thereof.

Preferably, this or these solvent compounds have the property ofdissolving the other ingredients of the ink, in particular the binder,the dye stuffs, additives, etc.

The alcohols are preferably chosen from among straight-chain or branchedaliphatic alcohols with 1 to 8 carbon atoms, such as methanol, ethanol,propanol-1, propanol-2, n-butanol, butanol-2, tert-butanol, etc.

The ketones are preferably chosen from among the ketones with 3 to 10carbon atoms, such as acetone, butanone (methyl-ethyl-ketone),pentanone-2 (methyl-propyl-ketone), methyl-3 butanone-2 (methylisopropylketone) and methyl-4 pentanone-2 (methyl-isobutyl-ketone).

The ethers of alkylene glycols are preferably chosen from among themono-alkyl ethers (C1 to C6 alkyl group) or dialkyl ethers (C1 to C6alkyl groups) of alkylene glycol comprising 1 to 10 carbon atoms in thealkylene chain, preferably they are ethers of ethylene or propyleneglycol, such as methoxy-propanol.

The esters of alkylene glycols and the esters of ethers of alkyleneglycols are preferably chosen from among the esters thereof withsaturated aliphatic, carboxylic acids with 1 to 6 carbon atoms, such asformic acid, acetic acid, propionic acid, butyric acid, valeric acid andcaproic acid.

For example, mention may be made of methoxypropyl acetate, butyldiglycolacetate, etc.

The esters are preferably chosen from among the esters of low molecularweight such as the formiates, acetates, propionates or butyrates ofalcohols with 1 to 10 carbon atoms.

The acetals are preferably chosen from among the acetals of lowmolecular weight such as ethylal and methylal.

The ethers are preferably chosen from among the ethers of low molecularweight such as dioxolane or tetrahydrofuran.

The man skilled in the art will easily be able to identify among thesesolvent compounds those which are volatile and those which arenon-volatile.

One preferred solvent according to the invention consists of one or moreketone(s) such as Methyl-Ethyl-Ketone (MEK).

The ink composition of the invention may also comprise a bindercomprising one or more polymer(s) and/or resin(s).

These polymer(s) and/or resin(s) are preferably chosen from among the(meth)acrylic, vinylic, ketonic, hydroxyaromatic, cellulosic, styrenic,epoxy resins, the polyurethanes, the styrene-acrylates, thealkoxysilanes, and the combinations of two or more thereof.

Examples of These Resins Are the Following

For the acrylic, methacrylic and styrene-acrylate resins, the Joncryl®resins by BASF, Paraloid® resins by DOW, SMA® resins by ATOCHEM orNeocryl® resins by DSM.

For the vinylic resins, the Hostaflex® resins by CYTEC, Vinylite® resinsby UNION CARBIDE or Vinnol® resins by WACKER.

For the ketonic resins, the products available from HULS and BASF, suchas the so-called AP and SK resins by HULS and LAROPAL® resins by BASF.

For the phenolic resins, the products offered by CYTEC under the tradename ALNOVOL®.

Among the cellulosic resins, such as the nitrocelluloses,ethylcelluloses, cellulose aceto-propionates or aceto-butyrates resins,mention may be made of the products offered by AQUALON or EASTMAN.

Among the epoxy resins, the Epikote® resins by SHELL can be cited or theAraldite resins by CIBA.

Among the polyurethanes, mention may be made of the Surkopak® resins byMITCHANOL.

Hydroxyaromatic resins are defined and described in documentWO-A-2010/103088 and reference can be made to the description thereof.Preferred resins are the hydroxyphenolic or phenolic resins.

It is specified that by hydroxyphenolic resin or simply phenolic resinis generally meant any polymer comprising phenol OH groups.

Advantageously, the hydroxyphenolic resins may be chosen from among thenovolac resins and the polymers of hydroxystyrene.

The resins of novolac type are derived from the polycondensation of aphenol and formaldehyde in the presence of an acid catalyst.

By polymers of hydroxystyrene is meant the homopolymers ofhydroxystyrene and the copolymers of hydroxystyrene with other monomerssuch as the (meth)acrylates.

Said polymers are particularly described in documents WO-A-98/13430 andUS-B1-6,251,175 to which reference may be made.

Alkoxysilanes are defined and described in document WO-A-2010/103088 towhich reference may be made.

These alkoxysilanes may be aminoalkoxysilanes in particular, which arealso defined and described in document WO-A-2010/103088 to whichreference may be made.

Advantageously, said aminoalkoxysilane may be chosen from among:gamma-aminopropyltriethoxysilane, gamma-aminopropyltrimethoxysilane,N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane,3-aminopropylmethyldiethoxysilane, 3-aminopropyldiisopropylethoxysilane,3-(1,3-dimethyl butylidene) aminopropyl-triethoxysilane, andbis-(trimethoxysilyl propyl) amine.

One preferred binder according to the invention comprises thecombination of at least one alkoxysilane with at least onehydroxyaromatic resin such as a novolac resin.

However, in the composition of the invention, the binder is not obtainedby reaction between the alkoxysilane and the hydroxyaromatic resin byheating for example. Since an ionic liquid is used in the ink of theinvention, it is not necessary to cause these two compounds to reacttogether e.g. by heating in order to obtain a binder which gives amarking having water-resistance (see Examples 2 and 3), whereas this isnecessary with the composition of document WO-A-2010/103088 (seecomparative Example 2).

The proportion of binder in the ink composition of the invention isgenerally from 0.1 % to 30 % by weight, preferably 1 % to 25 % byweight, more preferably 3 % to 20 % by weight of the total weight of theink composition.

The ink composition may further comprise one or more plasticizer(s) (ofthe resin(s) or polymer(s) of the binder) chosen for example from amongplasticizers known to the man skilled in the art and chosen in relationto the binder used comprising one or more polymer (s) and/or resin(s);as plasticizer mention may be made for example of the thermoplasticpolyurethanes, phtalates, adipates, citrates, or the alkyl phosphates.

By means of the widely varying choice of possible solvents for thecompositions of the invention, it is easily possible to incorporate saidplasticizer compounds in the composition of the invention by choosingthe suitable solvent(s) .

The plasticizer(s) are generally present in the proportion of at least0.05 % by weight, preferably 0.1 % to 20 % by weight of the total weightof the ink composition.

The dye(s) and/or pigment(s) may be chosen from among all the dyes andpigments suitable for the intended use, known to the man skilled in theart; some of these pigments or dyes have already been mentioned above.

In general the dyes and pigments may be chosen from among the dyes andpigments known under the name « C. I. Solvent Dyes » and « C. I.Pigments ».

As examples of the most common pigments and dyes mention may be made ofC. I. Solvent Black 29, C. I. Solvent Black 7, C. I. Solvent Black 28,C. I. Solvent Black 27, 35 and 45, C. I. Solvent Blue 70, C. I. SolventRed 124, the dispersions of Pigment Blue 60 or of Pigment Blue 15.

One preferred dye is C.I. Solvent Black 29.

The total quantity of dye(s) and/or pigment(s) is generally 0.05 % to 25% by weight, preferably 1 % to 20 %, more preferably 3 % to 10 % byweight of the total weight of the ink composition.

Preferably a dye is chosen having the lowest solubility in water, whichis water-insoluble.

By water-insoluble dye is generally meant a dye which, when added at 1 %to demineralised water, does not cause colouring of the water that isvisible to the eye.

Again, by means of the wide variety of solvents which can be included inthe ink composition of the invention, it is possible to choose thesesolvents so that they are able to dissolve the dye or dyes, and inparticular the dyes that have most water-resistance, in larger quantitythan in usual solvents; it is particularly possible, with a fluorescentdye to obtain inks that are particularly fluorescent i.e. visible underlow UV illumination.

The ink composition of the invention being sprayable by continuousink-jet, it must have sufficient conductivity, generally equal to ormore than 5 pS/cm at 20° C., preferably equal to or more than 300 pS/cmat 20° C., more preferably equal to or more than 500 pS/cm at 20° C.

The conductivity of the ink composition according to the invention mayrange from 5 to 5000 pS/cm for example, in particular from 500 to 2000pS/cm (at 20° C.) .

The products which impart the necessary conductivity to the ink forcontinuous deflected ink jet printing, are according to the inventionionic liquids.

However, it is possible that the dye(s) and/or pigment(s) alreadypresent in the ink impart some degree of conductivity to the inkcomposition, which means that it is possible to reduce accordingly thequantity of ionic liquid(s) to be included in the ink composition inorder to reach the desired conductivity. Said dyes and/or pigments areespecially the compounds known under the name « C. I. Solvent Black 27,29, 35 and 45 », already mentioned above.

When the markings obtained with this composition have to be waterresistant, the ionic liquids will be chosen, as already mentioned above,from those which are the most insoluble in water.

The composition according to the invention may, in addition, compriseone or more additives chosen from compounds which improve the solubilityof some of its components, the print quality, the adhesion, or else thecontrol of the wetting of the ink on various substrates, supports.

The additive (s) could be chosen, for example, from anti-foaming agents;chemical stabilizers; UV stabilizers; surfactants, such as Fluorad® FC430 or Byk® 333; agents that inhibit salt corrosion; bactericides,fungicides and biocides; and pH control buffers, etc.

The additive (s) is (are) used in very low doses, in general less thanor equal to 5% and sometimes as low as 0.01%, depending on whether theyare anti-foaming agents, stabilizers or surfactants.

The invention also relates to a process for marking substrates, supportsor objects by spraying an ink onto these substrates, supports or objectsby the continuous deflected jet technique, in which the ink sprayed isthe ink composition according to the invention, as described in theaforegoing.

The invention also relates to a substrate, support or object providedwith a marking obtained by drying and/or absorption (in the support,substrate, object) of the ink composition according to the invention.

This substrate may be made of metal, for example, aluminium or steel;made of glass; made of ceramic; made of a material containing cellulosesuch as paper, optionally coated or glossy, glazed, enameled paper,cardboard or wood; made of a synthetic polymer (“plastic”) especially inthe form of films, such as PVCs, PETs, polyolefins such as polyethylenes(PEs), or polypropylenes (PPs); made of polymethylmethacrylate(Plexiglas®) ; made of fabric; or made of any other non-porous or poroussubstance ; or made from a composite of several of the precedingmaterials.

This substrate may be porous or non-porous.

This substrate may especially be a container or vessel such as a glassbottle.

Markings, printings of excellent quality are obtained on all substrates,even scarcely porous substrates.

The invention will be better understood on reading the followingdescription of embodiments of the invention given as illustrative,non-limiting examples.

EXAMPLES

The following ink compositions according to the invention were preparedby mixing the products given in Table I below in the indicatedproportions. The viscosities and conductivities of the inks obtained arealso given below.

The viscosities were measured using a Low-Shear 30 coaxial cylinderviscometer by Contraves (Switzerland) at 20° C., and conductivities weremeasured at ambient temperature, generally 20° C.

Table I Examples (weight percentages) Comparative Example 1 ComparativeExample 2 N°1 N°2 N°3 N°4 Methyl ethyl ketone 64.25 72.4 64.25 69.4970.56 70.56 LTH resin by HULS 2.0 2.0 Resamine HF480 13.7 13.7 SolventBlack 29 6.15 5 6.15 4.37 4.91 4.91 Acrylic resin (Joncryl 690 by BASF)8.8 8.8 Aminopropyltrimeth oxysilane 2 1.75 1.96 1.96 Phenolic resin ofnovolac type 20 22.99 19.63 19.63 Polyester resin (Reactol 545 byHexion) 4.4 4.4 Potassium hexafluorophosphat e 0.6 0.51-butyl-3-methylimidazolium hexafluorophosphat e 0.6 1.31 2.941-butyl-3-methylimidazolium tetrafluoroborate 2.94 Tegoglide 435 0.1 0.1Byk UV 3500 0.1 Tegophobe 6000 0.09 Viscosity (mPa.s) 5.16 4.56 5.184.58 5.45 5.83 Conductivity (µS / cm) 705 780 613 716 883 1218

The ink compositions of the invention prepared according to Examples 1to 4, and also those of comparative Examples 1 and 2, were filtered onfilters having a porosity of 1 µm, and gave inks that can be sprayed byink-jet.

The inks thus prepared were tested on Markem-Imaje® printers of type9040 which operate according to the principle of continuous deflectedink jet printing.

The markings, printings obtained with the inks of Examples 1 to 4 andcomparative Examples 1 and 2 were all of excellent quality and theirresistance to rubbing with water on glass was excellent.

However, the resistance of the printing obtained with the inkcomposition according to the invention of Example 1 was better than theresistance of the printing obtained with the ink of comparative Example1 which does not contain an ionic liquid.

Also, and contrary to the indication given in document WO-A-2010/103088,the water resistance of the printing obtained with the ink compositionsof the invention of Examples 2 and 3 containing an ionic liquid isobtained without heating the complete solution, whereas with the ink ofcomparative Example 2 it is necessary for the formulation to be heatedso that the printing obtained are resistant to rubbing with water onglass.

What is claimed is:
 1. An ink composition for continuous deflected inkjet printing, liquid at ambient temperature, comprising: a) a solventcomprising, preferably consisting of, one or more organic solventcompound(s), and optionally water, the said solvent representing atleast 20 % by weight of the total weight of the ink; b) at least onecompound imparting conductivity to the ink composition, chosen fromamong ionic liquids, the said compound representing 0.2 % by weight to 4% by weight of the total weight of the ink composition, preferably 0.5to 3 % by weight of the total weight of the ink composition; and the inkcomposition comprising less than 10 % by weight, preferably less than 5% by weight, more preferably less than 1 % by weight, and mostpreferably 0 % by weight of water relative to the total weight of theink composition.